Within the food industry, beverages and other products are often packed in paper or paperboard based packages. Packages intended for liquid food are often produced from a packaging laminate comprising a relatively robust core layer of paper or paperboard and an outer, liquid-tight layer of thermoplastic material on at least that side of the core layer which will form the inside of the packages. For particularly oxygen sensitive food products, such as fruit juice and cooking oil, the packaging laminate usually further comprises a layer of a gas barrier material. This layer is in most cases an aluminum foil which also enables induction sealing of the packaging laminate.
The packages are often produced in a packaging machine where a web of packaging laminate is formed into a tube which is closed by sealing of the longitudinal edges of the web in an overlapping condition. The longitudinally sealed tube is continuously filled with a product and then transversally sealed, wherein filled “cushions” are formed. The transverse sealing is made along narrow, transverse, mutually spaced apart, sealing zones. After the transverse sealing, the “cushions” are separated from the rest of the tube by incisions in the sealing zones and finally formed into the desired shape. The “cushions” can, as an example, be formed, by mechanical folding, into parallelepiped-shaped packages like the ones commercialized by the applicant under the name Tetra Brik or Tetra Brik Aseptic (registered trade marks).
A packaging machine of the above type is known from U.S. Pat. No. 4,580,392. This packaging machine comprises alternately working forming and sealing jaws which are given a reciprocating movement in the longitudinal direction of the tube and in the transverse direction of the tube. The sealing jaws are guided and driven by guiding and driving rods which run parallel to the tube and to which different reciprocating movements are imparted. Attached to the sealing jaws are forming flaps determining the shape of the finished packing container and therefore also its volume.
Packages are often provided with an opening device for facilitating consumption of the product in the package. Different types of opening devices can be used, for example an opening device comprising a frame fitted to the top wall of the package and defining an opening of the same, and a removable cap hinged or screwed to the frame. The top wall of the package formed from the tube of packaging laminate will comprise a number of seals resulting from the longitudinal and transverse sealing. Because of technical difficulties, it is not preferred to arrange the opening device in an area of a seal. Therefore, the amount of space available for positioning of the opening device on the top wall of the package is quite limited. As an example, in the case of a Tetra Brik package, the top wall is centrally crossed by a transverse seal. Further, an end portion of the longitudinal seal extends centrally across half the top wall, perpendicularly from the transverse seal. Obviously, this limits the maximum size of the opening device used. However, in many situations a relatively large opening device is desired. As an example, when the product to be packed is semiliquid or contains fibres or larger particles, a bigger opening device is required to enable smooth pouring of the product.
Further, an opening device usually protrudes from the package which may be drawback when it comes to stacking of the package. As an example, in the case of Tetra Brik packages provided with a respective opening device on the top wall, stacking of the packages on top of each other may be difficult. In a stack, the uppermost package will be supported by the opening device on the second uppermost package and so on. Obviously, this is not a stable configuration, especially since the opening device, as apparent from above, is arranged off-center at the top wall and has a limited size.
To increase the space available for positioning of the opening device on the top wall of the package it has been proposed to provide the front edge of the top wall of the package, which front edge is opposite the edge of the top wall crossed by the longitudinal seal, with a convex C-shaped bend line or so-called “smile crease”, instead of a straight one. However, a package produced in accordance with this solution will naturally not have the shape of a perfect parallelepiped because of the increased top wall area. Instead, the front side wall of the package, which is adjacent to the front edge of the top wall, will be projecting in an area close to the C-shaped bend line. Further, the top wall will be sloping downwards from the transverse seal to the C-shaped bend line. The more convex the bend line is, the more the package will differ from the parallelepiped-shape. Thus, the purpose of the C-shaped bend line is to enable the provision of a relatively large opening device on the package. With such a relatively large opening device, the above discussed stacking problems will most likely still be present. Further, there may also be problems relating to stowing of these “smile crease” packages in rows with the front side wall of one package facing the opposite back side wall of the neighboring package because of the projection of the front side wall.